Stimulatory mechanisms of cholecystokinin secretion by food peptides in enteroendocrine cells

Abstract

Background We previously found that an arginine-rich peptide derived from soybean beta-conglycinin stimulates cholecystokinin (CCK) secretion from the isolated rats mucosal cells of the small intestine and a cultured CCK-producing enteroendocrine cell line, STC-1. The aim of the present study was to clarify the stimulatory mechanisms for CCK secretion by food peptides derived from legumes. Methods STC-1 cells were cultured with DMEM for 2 days after seeding, and was loaded Fura2-AM to observe intracellular Ca signals after application of soybean beta-conglycinin peptone (BconP). Released CCK was measured with an ELISA kit. Various cellular signal blockers or Ca deprived medium were used to determine signaling pathways for induction of Ca signals and CCK secretion. Results and conclusion Application of BconP induced dose-dependent intracellular Ca signals and CCK release from STC-1 cells. Deprivation of extracellular Ca partly suppressed Ca signals, but not CCK secretion. Cell permeable Ca-chelator BAPTA-AM and Gaplha-q inhibitor YM254890 reduced CCK secretion induced with BconP, which indicates that BconP stimulates CCK secretion dependent on induction of Ca signals derived from intracellular Ca store via a G-protein coupled receptor (GPCR). Adenylate cyclase inhibitor, DDA, also reduced CCK secretion stimulated with BconP without any changes in Ca signals. These results demonstrate that BconP binds to unknown GPCR and other receptors, and activates both Ca-dependent and-independent intracellular signaling pathways to release CCK in the enteroendocrine cells. We also found another legume-derived peptide with much stronger potential for CCK secretion.